A polarizing microscope has been altered to allow optical spatial filtering to be accomplished. The alterations permit a spatial filter to be placed near the back focal plane of the microscope objective and a laser is used as a light source. The instrument can be used to focus on a specimen as would be done for any ordinary application of the microscope, or the standard Amici-Bertrand lens can be used to focus on the Fourier transform of the specimen. For a low power objective, the field of view of the specimen is about one centimeter and the spatial frequency passband is about one hundred lines/mm. The image of the specimen, its Fourier transform, the filtered transform, and the filtered image can each be viewed or photographed using this simple instrument.